Lithium niobate (LN), as one of the most widely studied optical materials, has played a significant role in nonlinear optics [1]} for its rich and favorable optical properties [2]}. One unique characteristics of LN is the photorefractive (PR) effect, which arises as a combination of the photo-excited space-charge field and the subsequent electro-optic effect, inducing a refractive index variation during light illumination [2]}, [4]}. In the past decades, vast amount of research has been performed to study and control this important feature of LN crystals [5]}, [6]}, [7]}. On one hand, the PR effect is considered to be responsible for the optical damage [6]}, introducing instability and limiting the power handling capability of devices [7]}, [10]}. On the other hand, the photorefractive effect could also be utilized for optical holography and storage [11]}, [12]}.
